Aviation trainer



Oct. 18, 1949. K. A. KAlL 2,485,292

AVIATION TRAINER Filed Sept. 29, 1945 12 Sheets-Sheet 1 FIG.|

KARL A. KAI L INVENTOR.

W4. ATTQRN s l Oct. 18, 1949. K. A. KAI L AVIATION TRAINER 12 Sheets-Sheer. 2

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AVIATION TRAINER Filed Sept. 29, 1945 l2 Sheets-Sheet 3 h KARL A. KAIL v INVENTOR.

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12 Sheets-Sheet 7 Filed Sept. 29, 1945 WWW ATTO RNEYS Oct. 18, 1949. K. A. KAIL AVIATION TRAINER 12 Sheets-Sheet 8 Filed Sept; 29, 1945 KAIL KARL A.

INVENTOR.

Oct. 18, 1949. KAIL 2,485,292

AVIATION TRAINER I a .550 526 g 57 I a 35 $449 64 5' 542 J36 53753762 v w 525 g I 2 I 1 6 1 1\\ m 2 Q 547 3 54 4 5&0 4% 3? KARL A. KAI L A INVENTOR T546 Q FIG. u BY y/{M Oct. 18, 1949.

Filed Se'pt. 29, 1945 K. A. KAlL 2,485,292

AVIATION TRAINER 12 Sheets-Sheet 1O WVEm-OW f 42 AT'ro EYS Oct. 18, 1949. K.A.KAIL 2, 85,292

Avm'rIbN TRAINER Filed Sept. 29, 1945 l2 sh e ts- -sheet 11 KARL A. KAI L 11w EN TOR;

Oct. 18, 1949. A, KAlL 2,485,292

AVIATION TRAINER Filed Sept. 29, 1945 12 Sheets-heet 12 FIG. ISA

KARL A. KAIL INVENTOR.

Patented Oct. 1 8, 1949 AVIATION TRAIN ER Karl A. Kail, Montrose, Pa., assignor to Link Aviation, Inc., a corporation of New York Application September 29, 1945, Serial No. 619,361

23 Claims.

This application, which is a continuation in part of my application Serial Number 601,776, filed June 27, 1945 for Simulated flight control loading and centering means for grounded aviation trainer relates to improvements in grounded aviation trainers which are widely used to instruct students in the art of flying aircraft,- and will be illustrated in connection with trainers of the type disclosed in U. S. Patents 1,825,462 and 2,099,857. However, it will be appreciated that many of the improvements disclosed herein are applicable to other types of trainers, and the incorporation of my improvements in such trainers is intended to be covered hereby.

While trainers of the type disclosed in the above mentioned patents have been widely used with great success by the Army, Navy and civilian agencies, as well as by private organizations, the trainers known to the prior art were frequently criticised as not having the feel of an airplane. It is true that the prior art trainers could be turned by the simulated rudder pedals,- banked by the simulated aileron control and pitched by the simulated elevator control, and also, the prior art trainers incorporated such features as turn with bank, bank with turn, nose down with turn, and turn tightening. However, many of the characteristics of an aircraft in flight were not present in such trainers. For example, in the flight of aircraft the engine power output produces a torque which tends, conventionally, to increasingly turn the plane to the left as the engine power and resultant torque increase. Also, an increase in air speed produces a tendency of the plane to turn to the right, while a decrease in air speed lessens this tendency.

At the same time, an increase or decrease in engine power output causes the plane to hunt, and when the hunting has tapered out, the nose of the plane will be higher or lower, depending upon whether the power output was increased or decreased.

The above described torque and change in attitude as a result of a change in power output may, in most planes, be counteracted by the use of the trim tab controls provided in airplanes of the type which the trainers being considered simulate.

Also, a plane in actual flight will hunt about its transverse axis if the plane is placed in a climbing or diving position and the elevator control is then released.

In the case of a plane in actual flight, the plane will automatically turn in the direction of bank, but if sufiicient opposite rudder is ap- 2 plied to prevent the plane from turning when it is banked, the inherent stability of the plane will cause the plane to assume level transverse flight.

It is an object of this application to disclose means in a grounded aviation trainer for simulating the previously outlined responses of planes in actual flight, in addition to retaining the listed prior art features of such trainers.

The prior art trainers also included a simulated air speed indicator responsive to the throttle lever setting and pitch attitude of the trainer fuselage. This application discloses means whereby the simulated air speed indicator indicates in accordance with the combined factors of pitch attitude and assumed manifold pressure or simulated engine output. In turn, the assumed manifold pressure is made a function of the combined factors of throttle lever setting, propeller governor control lever setting and assumed altitude. Assumed altitude is made to depend upon the factors of fuselage attitude and assumed air speed. Thus, assumed air speed affects assumed altitude which in turn affects assumed air speed through its influence on manifold pressure. These changes in the air speed and altitude systems are deemed to be important contributions to the art.

This application also discloses many other improvements such as cam operated instrument control valves, improvements to the conventional rudder valve, a mush valve for venting the altitude system to simulate a loss of altitude as a result of a loss of air speed, and means for simulating the difference between true and indicated air speeds. Also, a new method of centering the conventional climb-dive valves is disclosed.

In order that the exact nature of the improvements herein disclosed may be better understood, reference is made to the accompanying drawings, wherein Fig. 1 is a general view of a grounded aviation trainer of the type being considered showing the general location of many of the major parts of this invention.

Fig. 2 is a detailed perspective view of the elevator control loading system, together with the elevator trim system.

Fig. 2A is a detail view showing the construction of the elevator and aileron control loading bellows.

Fig. 2B is a detailed exploded View of a typical control loading centering valve which may form a part of my invention.

Fig. 2C is a detailed showing of a typical control loading regulator bellows.

Fig. 2D is a detailed showing of a compensating spring arrangement which may be used in the practice of my invention.

Fig. 2E is a detail view of the cam arrangement shown generally in Fig. 2.

Fig. 3 is a detailed showing of the aileron control loading and trimming means.

Fig. 3A is a detailed view of the cam arrangement shown generally in Fig. 3.

Fig. 4 is a detailed showing of the rudder pedal loading and trim system.

Fig. 5 is a detailed perspective view of the universal joint and associated parts.

Fig. 6 is a perspective view showing the general relationship of many of the control systems of this invention.

Fig. '7 is a detailed exploded view of the construction of the main fuselage control valves.

Fig. 7A is a bottom view of the top leaf of the rudder valve.

Fig. 8 is a schematic view of the air speed system.

Fig. 9 is a detailed drawing of the manifold pressure unit.

Fig. 9A is a detailed showing of the switching arrangement of the apparatus shown in Fig. 9.

Fig. 10 is a schematic view of a portion of the manifold pressure system.

Fig. 11 is a cross-sectional view of a typical instrument control valve.

Fig. 12 is a schematic view of the altitude system.

Fig. 13 is a detailed drawing of the altitude torque amplifier.

Fig. 14 is a detailed drawing of the air speed unit and trim compound differential.

Fig. 15 is a drawing of a portion of the air speed system.

Fig. 16 is a showing of a portion of the trainer base, wind-drift unit, desk and recorder.

Fig. 17 is a detailed perspective view of the mush valve and air speed control loading regulator bellows.

Fig. 18 is an exterior drawing of the climbdive valve assembly.

Fig. 18A is a detailed drawing of the cam associated with the climb-dive valves.

General description of trainer Reference is now made to Fig. l which is a general disclosure of grounded aviation trainers of the type covered by U. S. Patents 1,825,462 and 2,099,857. Such trainers comprise a stationary base l0 above which is mounted a fuselage l2 simulating the fuselage of an actual aircraft. Within this fuselage there is a seat for a student positioned to the rear of the control wheel 30. The fuselage I2 rests upon a universal joint 14, shown in detail in Fig. 5, and this joint is supported by the pedestal l3 which is held by the main central vertical spindle 15 which is rotatably held by the stationary base Ill. The conventional octagon is designated by It and as is well known to the prior art, octagon I6 is affixed to the main spindle l5 below the universal joint l4 and pedestal 13 by means of suitable horizontal arms Ilia seen in Fig. 5 so that the octagon it rotates with the pedestal l3, spindle l5, universal joint I4 and fuselage l2 relative to the stationary base ID.

A forward pitching bellows l1 and a rearward .pitching bellows l8 are provided, the bottom the other hand the admission of vacuum to the rear bellows l8 and of atmosphere to the fore bellows l1 causes the fuselage I2 to assume a climbing attitude. As will be more fully explained later, the admission of vacuum and at- I mosphere into the bellows l1 and I8 may be controlled by the student in the trainer by moving the control wheel 3i] fore and aft of the fuselage [2, so that the student may control the diving and climbing position of the fuselage I2. The diving and climbing position of the fuselage are sometimes referred to hereinafter as pitching.

At the same time, trainers of this type have a left banking bellows H! as well as a right banking bellows 20 upon the opposite side of the universal joint i l from the bellows l9. [he admission of vacuum and air into these bellows may be controlled by the student through a rotation of the control wheel 30 so that he may place the fuselage 152 in any desired banking position within the limits of the apparatus.

Trainers 0f the type being considered are often equipped with a stick instead of a control wheel, and it will be readily apparent to those skilled in the art, after reading this specification, that they can substitute a stick for the wheel to and still obtain all of the advantages of my invention.

Fixedly carried by the octagon iii are the horizontal arms 2i which support the turning motor 22. By means of a Well known pulley arrangement connecting the turmng motor 22 with the stationary base it), the student in the fuselage [2 may, by pressing either of the rudder pedals 256, energize the turning motor 22 in such a direction that the turning motor 22, supporting arms 2|, octagon l6, supporting arms Ilia, bellows ll, l8, l9 and 20, spindle It, pedestal l3, universal joint l4 and fuselage l2 will rotate either to the left or right, as desired, relative to the stationary ibase Ill. Thus the student may control the simulated heading of the fuselage 12 in the same manner that he would control the heading of a plane in actual flight. The arms 25 are attached to the octagon and support the housing 25a in which may be placed a vacuum pump for operating the instruments in the trainer, as will be later more fully explained.

The steps 26 and door 26a allow access to the interior of the fuselage l2 and a slidable canopy 21 may be used to completely encompass the cockpit of the fuselage lz in order to simulate blind flying conditions. The canopy '2! may be made of a suitable translucent material in order to permit enough light to enter the cockpit of the fuselage to enable the student to manipulate the trainer without the assistance of artificial lights placed in the interior of the fuselage. Such conditions closely simulate day-time blind flight conditions. On the other hand when it is desired to simulate night-time blind flying conditions, a suitable opaque material such as a cover may be placed over the canopy 21 in order that no light enters the cockpit through this canopy.

The student must then rely upon the conventional artificial lights which are placed inside the cockpit. Such an arrangement closely simulates night-time blind fiying conditions.

An instrument panel 29 is inside the fuselage and upon this panel are instruments which simulate the instruments carried by actual aircraft. As is well known to the prior art, and as will be later explained more in detail, these instruments operate in response to simulated conditions just as the corresponding instruments in a real plane react to real flight conditions.

Simulated elevator control loading and trimming means Referring now to Fig. 2, it will be seen that the control wheel in the fuselage is designated 38 and that this wheel is fixedly mounted upon the rear end of the forwardly extending shaft 32. As will become clear later in the description, the fore end of the shaft 32 is mounted in a bracket carried by the fuselag so that the shaft 32 may move axially. A pair of collars 34 are afiixed upon shaft 32 as shown so that axial movement of the shaft 32, caused by the students pushing or pulling the wheel 38, results in a pivoting of the upstanding members 38 which are pivotally mounted at their lower ends upon the horizontal transverse shaft 40 which is fixedly held by the bracket 42 mounted upon the floor of the fuselage as seen in Fig. 1. The upstanding members 38 are positioned with respect to one another by the crosspieces 44 and 46.

In Fig. 2 it will be seen that integral with the fixed bracket 48 are a plurality of upstanding members 48 which support a base plate (not shown) to which are attached the fixed, vertical, bellows supporting plates 58, these two plates being parallel and placed upon opposite sides of the elevator control loading bellows designated generally by 52.

Reference is now made to Fig. 2A which is a detailed disclosure of the construction of the bellows 52. In Fig. 2A it will be seen that the bellows 52 comprises a pair of end members 54 which are fixedly held by the plates 58 by means of screws 55. In the center of the bellows 52 is the main, generally upstanding, common bellowsforming member 56 pivoted at its :bottom end by means of the rod 5! held by the plates 58. It will be seen that between the member 56 and each of the end members 54 is a rigid wooden member 58 each having a plurality of holes 59 therethrough. Two substantially airproof, flex-- ible coverings 68 are provided, one on either side of the member 55 and attached thereto. In view of the described arrangement it will be appreciated that the bellows 52 in reality comprises two separate :bellows, each having one fixed end in the form of its associated member 54 and each having a common movable central member in the form of the member 56. The left bellows seen in Fig. 2A is designated 52a and is connected through the port BI and air-vacuum line with the three leaf elevator centering valve designated generally by 63. The right bellows in Fig. 2A is designated 52b and is connected through port 64 and vacuum-air line '65 with the elevator centering valve 63.

Reference is now made to Fig. 2B which shows the detailed construction of the elevator centering valve 63. As seen, this valve comprises a lower fixed leaf 66, a center movable leaf 6! and an upper movable leaf 68'. Referring to Fig. 2

it will be seen that the lower fixed leaf 66 is alfixed to the bracket 69 which in turn is affixed to the plates l8 and H which are affixed to the stationary side plates 58. Consequently the lower leaf 66 is fixed in relation to the interior of the fuselage [2.

Referring to Fig. 2B, it will be seen that fixedly mounted in the center of the lower leaf 66 is the vertical hollow stem 12 having a plug 13 in its upper end and a plurality of ports 14 in its side walls. Referring now to Fig. 2 it will be seen that the lower end of the hollow stem 12 is connected by means of the vacuum line 13 with the interior of the elevator control loading regulator bellows designated generally 74. The bellows 74 shown in detail in Fig. 20 comprises a lower fixed member 15 and an upper member 76 pivotally attached thereto. A suitable flexible, airtight covering 11 is provided. Attached to the upper pivoted member 18 is the plate lea to which the lower end of the spring I21 is connected. Fixedly attached to the upper bellows member 16 is the needle 19 and a seat 88 is affixed to the lower member 15. Seat 88 is connected through the vacuum line 8| to the airspeed regulator bellows shown in Fig. 2 and designated generally 82. The air speed regulator bellows is connected by vacuum line 83 to the well known turbine 84- shown in Fig. 1.

As will be later more fully explained, the air speed control loading regulator bellows 82, located as shown in Fig. l, is responsive to the climbing and diving movements of the fuselage [2 as well as to the simulated engine power output, so that the pressure within the air speed regulator bellows 32 is at all times inversely related to the assumed air speed of the fuselage. For convenience it may be stated that the higher the assumed air speed, the greater is the vacuum within the bellows 82.

Still referring to Fig. 2, the vacuum within bellows 82 manifests itself at all times in the central stem T2 of the lower fixed leaf 65 through the vacuum line 8 I, elevator control loading regulator bellows l4 and vacuum line '33, but as will later appear the bellows 14 controls the amount of vacuum in stem 12.

Referring to Fig. 23 it will be seen that a pair of vertical ducts 85 and 86 extend from the upper face of leaf 88 downwardly and partly through the leaf 85. Connecting with the duct 85 is the exterior port 85a which connects with the line 85 which, as seen in Fig. 2, connects with the right bellows 52b of the bellows assembly 52. Similarly, connecting with the duct 86 is the port 81 which connects with the line 62 which connects with the interior of the bellows 52a of the bellows assembly 52.

Referring again to Fig. 2B, it will be seen that the movable center leaf 61 has a central bore 88 adapted to receive the vertical stem 12 and that two ports 89 and 90 extend completely through the leaf 61. When the leaf til is assembled relative to the lower fixed leaf 66, leaf 6! being in the central or neutral position, the port 89 coincides exactly with the port 85 and the port 90 coincides exactly with the port 86.

In the upper movable leaf 68 are a pair of vertical duets BI and 92 which extend completely through the leaf 68. It will be appreciated that the upper ends of both of the ducts 9i and 92 are at all times connected with the atmosphere. Centrally located within the leaf 68 is the vertical bore 93 extending completely through leaf 58 and adapted to receive the stem 12 of the lower leaf. Communicating with the vertical bore 93 of leaf 68 is the transverse duct 94 which communicates and 99 on the other.

-"With the vertical duct 95 drilled in the lower face of the leaf 68.

- .When the three leaves of the valve shown in -Fig. 2B are in the neutral assembled position, it

ports 9| and 92 cannot pass into either of the ports 89 or 99 because there is no overlap between the ports SI and 89 on the one hand and ports 92 Consequently, when the leaves of the valve 63 are all in their neutral position, a slight amount of vacuum passes through the lines 62 and 65 into the bellows 52a and 52b, and the bellows are neutralized.

However, assuming that the upper leaf 68 is rotated counterclockwise from its neutral position, it will be appreciated that the vacuum port,

95 will engage the port 89 which in the neutral position engages the port 85 of the lower leaf 66.

At the same time the atmosphere port 92 will engage the port 99 which in the neutral position engages the port 86. Consequently, an increased amount of vacuum will be applied to the line 6-5 which connects with the interior of the bellows 52b and simultaneously atmosphere will be applied through the line 62 to the bellows 52a. The bellows 522) will therefore be contracted and the bellows 5211 will expand. The common central member 56 will have a force applied thereto tending to move it to the right in Fig. 2 and by means of the clamping arrangement 51 and rod 44 the upper ends of the members 38 will tend to move toward the head of the fuselage. The shaft 32 and wheel 39 will have a force applied in the same direction.

On the other hand, it should be understood without a detailed explanation that when the three leaves of the valve 63 are in the neutral position, a clockwise movement of the upper leaf 68 will apply increased vacuum to the bellows 52a and atmosphere to the bellows 52b. The common central member 59 will have a force applied thereto tending to move it to the rear of the fuselage, and the shaft 32 and wheel 39 will have a tendency to move in the same direction.

Further, assuming that the leaves are in the neutral position and that the upper leaf 68 is moved counterclockwise to admit increased vac: uum to the bellows 52b and atmosphere to the bellows 52a, it will be appreciated that a corresponding counterclockwise rotation of the center leaf 6'! will shut off the passage of increased vacuum to the bellows 52b and will, at the same time, shut off the passage of air to the bellows 52a. The vacuum leak through the leaves when they are neutrally positioned will quickly neutralize the bellows 52a and 52b. On the other hand, with the leaves in their centralposition, should the upper leaf 68 be rotated clockwise to apply increased vacuum to the bellows 52a and air to the bellows 52b, a corresponding clockwise rotation of the center leaf 6'! will shut off the passage of excess vacuum to the bellows 52a and air to the bellows 52b, and thetwo bellows will quickly become neutralized.

Referring again to Fig. 2, it will be seen that integral with the upper leaf 68 is the horizontal extension 96 which is pivotally connected by 'means of the stud 91 to the ball joint 98 affixed upon the forward end of the link 99. Aflixed upon the link 99 is the stop I99 against which the forward end of the spring I9I compresses. Referring now to Fig. 2D, it willbe seen that the rear end of spring I9I presses against the washer I92 encircling link 99. Integral with the link 99 is the enlarged portion I93 and encircling this enlarged portion is the sliding sleeve I94. A second washer I95 encircles link 99 and the fore end of a second spring I96 bears against washer I95. Stop I91 aifixed upon link 99 positions the rear end of spring I96. Referring now to Fig. 2, it will be seen that the common bellows member 56 is attached to the sliding sleeve I94 so that the sleeve moves with member 56.

Assuming that the elevator centering valve is in the neutral position, in view of the preceding discussion it will be appreciated that the common bellows member 56 will also be in its neutral position. Consequently the bellows 52a and 52b will be neutralized. Now assuming that the student in the trainer desires to place the fuselage in a diving position, he will push the wheel 39 toward the head of the fuselage. The vertical members 36 will pivot about the rod 49, the upper ends of these members moving in the same direction as the wheel, and the upper end of the common be'llows member 56 will also move toward the head of the fuselage. Sleeve I94 moves in the same direction compressing spring IM and the compression of this spring acting upon the stop I99 moves the link 99 in the same direction. The upper valve leaf 68 will be rotated clockwise as seen from above and according to the previously explained operation of this valve, excess vacuum will be admitted to the bellows 52a and atmosphere will be simultaneously admitted to the bellows 5212. This admission of excess vacuum and air to these two bellows occurs as soon as the wheel 39 is pushed ahead of its neutral position. It will be appreciated that the admission of vacuum into the bellows 52a will tend to collapse the bellows 52a and the air admitted to bellows 52b will tend to expand the bellows 52b. Consequently a force resisting the forward movement 'of the wheel 39 will be immediately present. This closely simulates the loading placed upon the wheel of a plane in actual flight when the wheel is moved ahead of its neutral position.

When the wheel 39 is in its neutral fore and aft position, the valve 63 is in its neutral position. Should the wheel 39 then be moved by the student to the rear of the neutral position, the upper leaf 68 is rotated in the counterclockwise direction. Simultaneously, excess vacuum is applied to the forward bellows 52b and atmosphere to the rear bellows 52a. Thus a force is immediately present to resist the movement of the wheel 39 rearward from its neutral position, just as in the case of a plane in actual flight.

Assuming that with the wheel 39 and valve 63 in their neutral positions, the student pulls back on the wheel 39, excess vacuum is admitted to the forward bellows 52b and atmosphere to the rear bellows 52a. If then the student merely releases the wheel 39, the vacuum in the bellows 52b and atmosphere in the bellows 52a will move the common center member 56 toward the head of the trainer. The moving of the member 56 in this direction moves the wheel 39 ahead to its neutral position and simultaneously rotates the leaf '68 back to its neutral position. When the leaf 68 reaches its neutral position, the bellows 52a and 52b become quickly neutralized, and the wheel 30, member 56 and leaf 68 remain in their neutral positions. On the other hand should the student push the wheel 33 ahead of its neutral position, excess vacuum is admitted to bellows 52a and ail to bellows 521). If then the student releases the wheel 30, the bellows 52a and 52b move the member 56 and wheel 33 to the rear. The movement of member 56 simultaneously rotates leaf 68 to its neutral position, and when it reaches this position, the bellows 52a and 52b quickly become neutralized, and the wheel 30, member 56 and leaf 68 will be retained in their respective neutral positions.

In view of the foregoing disclosure the conclusion may be drawn that this invention discloses novel means whereby the control wheel 36 may have a force applied thereto tending to resist movement of the wheel in either direction from its neutral position. Also, when the wheel is moved from its neutral position and released, the wheel will return to its neutral position. Those skilled in the art of flying will appreciate that the bellows 52a and 52?) act upon the control wheel 33 in the same manner that the slip stream of a plane in actual flight acts upon the wheel in the plane through its effect upon the elevator of the plane, to which the control wheel is connected.

It will be appreciated by those skilled in the art of flying and in the field of aviation trainers that as soon as the student moves the wheel 30 to the rear of its neutral position, the fuselage I2 should assume a climbing position and that when the student moves the Wheel 33 ahead of its neutral position, the fuselage should assume a diving attitude. This response is obtained simultaneously with the loading of the wheel as described above by means of apparatus shown in part in Fig. 2. In that figure it will be seen that the link I l 6 is pivotally attached to the right vertical member 36 and the rear end of arm H6 is pivotally attached to the upper end of the lever Ill. Lever Ill is pivotally connected to the rotor of the shock absorber H2 which is fixedly mounted upon the upstanding members interal with the bracket -12. To the lower end of the lever H l is pivotally connected the forward end of the link M3. the rear end of which is pivotally connected, as seen in Fig. 6. to the lower end of lever I which is pivotally mounted upon the fixed rod 3b. To the upper end of lever ll3a is pivotally connected the rear end of link H30, the forward end of which is pivotel v connected to the outer end of arm l4 afiixed to the upper leaf 356 of the elevator valve designated generally by M5. Reference is now made to Fig. 7 which shows in detail the construction of the elevator valve H5.

In Fig. 7 it will be seen that there is rovided a hollow metallic manifold HM fixedl mounted within fuselage l2 and connected by means of the vacuum line lMb with the turbine 84 seen in Fig. 1. As seen. in Fig. 5. the vacuum connectinn HM? passes throu h t e universa ioint M and inside the main s indle l to the urbine. As seen in Fi 1. manifold HEP. is locat d to the ri ht of the universal joint M inside fuselage l2. Manifold MM is always evacua ed to a reduced pres ure by the turbine 8 or. as is often stated herein for convenience. is alwavs o i d with vacuum. In the center of the U er surface of the manifold U4. is the hole. 350. adahtffl to recei e in an. air-ti ht fashion the central tem 35' of the elevator valve H5. T e ow r lea-f of the elevator valve is designated 352 and this leaf 10 is fixedly mounted upon the top of manifold do by means of the screws 353 which fit into the top of manifold 4a by virtue of the tapped holes 354. Elevator valve H5 also comprises a center leaf 355 and a top leaf 356 and when assembled, the upper and lower flat surfaces of the center leaf 355 lie against the fiat lower surface of upper leaf 356 and the flat upper surface of leaf 352, respectively. The lower leaf 352 has two vertical ports 351 and 358 which open through the upper surface of leaf 352. Port 351 is in communication with the horizontal fitting 359 which is connected by means of the flexible tubing 366 which the forward pitching bellows I1 shown in Fig. 1. Similarly, port 358 communicates with fitting 36! which is connected by means of flexible tubing 362 with the rear pitching bellows l8, seen in Fig. 1.

Center leaf 355 of the elevator valve is provided with a central bore 363, the lower portion of which is adapted to fit around the boss 364 integral with lower leaf 352. A pair of vertical ports 365 and 366 extend completely through the center leaf 355. An arcuate counter-bore 361 is placed in the lower surface of center leaf 355, this counter-bore having one end commonly formed with the lower end of port 365. A second counter-bore 368 bears a similar relation to the leaf 355 and vertical port 366.

The upper leaf 356 is provided with an integral cylindrical boss 369 and a port 310 is drilled comnletely through the upper leaf. A plug 31| is inserted in the upper end of port 310. The upper portion of central stem 35I is provided with a plurality of ports 312 so that the central vertical port 316 of the upper leaf 356 is at all times supplied with vacuum. Communicating with the central port 31!) is the duct 313 which has an upper portion extending horizontally within leaf 356 and a lower vertical portion, also within leaf 356, communicating with the arcuate counter bore 314 placed in the lower face of leaf 356.

Also placed within the leaf 356 are the ports 315 and 316. Each of these ports has an upper horizontal portion emerging through the side of leaf 356 and a lower vertical portion emerging through the lower face of this leaf. Each of the ports 315 and 316 is therefore at all times in communication with the atmosphere.

In Fig. 7, the leaves 352, 355 and 356 are shown in. their neutral rotative positions. When the leaves are in their operative assembled position, the arcuate counter-bore 314 slightly overlaps the ports 365 and. 366. Also, the end of the counter-bore 361 slightly overlaps the port 351 and the end of counter-bore 368 slightly overlaps the port 353. Also. when the leaves are in their neutral positions. the lower end of port 315 is sli htly displaced from port 365 and the lower end of port 316 is slightly displaced from port 366. Conseouently, when the leaves of the elevator valve H5 are in their neutral positions the overla of counter-bore 314 with respect to the ports 365 and 366 and the overlap of counter-bores 361 and 363 with respect to the ports 351 and 358 result in the application of a limited amount of vacuum to both the forward and rear pitching bellows l1 and IS. The bellows l1 and 13 are therefore equalized and the trainer fuselage l2 is ongitudinally level.

It has been previously explained that the wheel 36 connected to the upper leaf 356 of the elevator valve I I5. At this point it may be stated that.

tional position. However, as seen in Fig. 2, when the wheel 30 is moved ahead of its neutral position, the link H3 moves to the rear. In Fi 6, the reversing action of lever II3a results in a forward movement of link I'I3c and the upper leaf 356 of the elevator valve is rotated clockwise from its neutral position. Accordingly, as seen in Fig. 7, the counter-bore 314 overlaps port 365 by a greater amount and increased vacuum is applied to port 365. Through counter-bore 361 this increase of vacuum is applied to port 351 and by means of connector 359 and tubing 36!] the increased vacuum is applied to the forward pitching bellows I1. Simultaneously therewith, the counter-bore 314 becomes out of engagement with the port 365 and the port 316 is brought into overlapping relation with the port 366. Atmosphere therefore is admitted to the port 366 and passes through the counter-bore 358, port 358, the connector 36I and flexible hose 362 to the rear pitching bellows I8. Consequently, a movement of the control wheel 30 ahead of its neutral position admits increased vacuum to the forward pitching bellows I1 and stops the application of vacuum to the rear bellows I8, applying to the rear bellows atmosphere. The forward bellows is therefore collapsed and the rear bellows is expanded, resulting in a lowering of thefore end of the fuselage I2 and a raising of the rear end of the fuselage. The fuselage therefore assumes a position simulating the diving attitude of a plane in actual flight. A real airplane, of course, assumes a diving attitudewhen the control wheel is pushed ahead of its neutral position.

On the other hand, assuming that the control wheel 30 is in its neutral position, the upper leaf 356 of the elevator valve II5 will be positioned in its previously described neutral. position. A rearward movement of the control wheel from the neutral position will result in a counterclockwise rotation of upper leaf 356, causing counterbore 314 to move out of overlapping position relative to port 365 and causing atmosphere port 315 to overlap port 365. Consequently atmosphere will be applied to the fore pitching bellows I1. Simultaneously, counterbore 314 will be brought into greater overlapping position relative to port 366 and greater vacuum will be applied to rear pitching bellows I8. Bellows I8 is collapsed, bellows I1 expanded, and fuselage I2 assumes a climbing attitude.

For future reference it might be underscored at this point that when the control wheel 3!! moves ahead of ts neutral position. the leaf 353 is rotated clockwise from its neutral position. and when the control wheel 3!! is moved to the rear of its neutral position. the leaf 356 is rotated counterclockwise from its neutral position.

Thus the conclusion may be drawn that as soon as the student in the fuselage moves the control wheel 30 ahead or to the rear of its neutral position. the uselage assumes the proper diving or climbing attitude. and that a force is present to resist the movement of the control wheel from its neutral position. both of which responses ocour in the case of a plane in actual. flight. Assuming that the student in the fuselage has moved the wheel 3!! from its neutral position, vacuum will be admitted to one of the bellows 520. or 521) and atmosphere to the other and the upper leaf of the elevator valve will be properly turned so that the fusela e will assume the correct pitchin (climbin or diving) attitude. In the absence of other factors. as will be later explained, if the student merely releases the wheel 3|], the bellows 52a and 5219 will return the wheel 30 to its neutral position and at the same time the upper leaf of the elevator valve will also be returned to its neutral position. Simultaneously the upper leaf 68 of the elevator centering valve 63 will be returned to its neutral position. Consequently the fuselage will assume the level flight position, the wheel will be returned to its neutral position and the loading upon the wheel will disappear. This closely simulates the three responses which occur when the pilot of a plane in actual flight, having moved the wheel from its neutral position, m'erely releases the wheel. The shock absorber H2 dampens the return of the control column to its neutral position under the influence of bellows 52.

Those skilled in the art of flying will appreciate that the load which is placed upon the control wheel in a real plane as it is moved fore and aft of its neutral position increases the farther the wheel is moved from the neutral position. Furthermore, this load increases with an increase in the air speed of the plane. This application also discloses means for simulating these two factors which affect the load upon the wheel of a plane in actual flight as the wheel is moved from its neutral position.

Referring again to Fig. 2, it will be seen that the rear end of the link I I6 is pivotally connected to the right upstanding member 38 and the forward end of this link is pivotally connected to the lower end of the lever II1 which is pivotally mounted upon the stud Illa held by bracket H. To the upper end of lever H1 is pivotally connected the link I I8, the fore end of which is pivotally attached to the upper end of the arm H9 which, as best seen in Fig. 2E, has its lower end pivotally attached to the plate 10 by means of stud I2il. A stud I2I is integral with the arm H9 and a slide I22 has two slots I23 therein. The studs I26! and I2I pass through the slots I23 in member I22. Another stud I24 is fixedly carried by the upper end of the slide I22 and carried by this stud is the cam roller I25. A cam I26 is pivotally carried by the stud I2!) and a spring I21 has its upper end attached to the lower end of slide I22, the lower end of spring I21 being attached to the extension 'I'Ia affixed upon the upper movable portion 16 of the bellows 1 5.

When the wheel 30 and the centering valve 63 are both in the neutral position, the cam roller I24 iscentered with respect to the cam I26 and therefore a minimum of tension is exerted upon the spring I21. Consequently the vacuum present within the bellows 14 is at a minimum, e. g., one inch. As soon as the wheel 30 is moved from its neutral position, not only is the upper leaf 68 of the centering valve 63 rotated so as to cause the bellows 52a and 52b to exert a force upon the wheel 30 resisting the movement of the wheel from. its neutral position, but simultaneously therewith the link H6 will be moved and through the operation of the lever H1 and link H8 the upper end of arm H9 will simultaneously be moved. The movement of the arm H9 will, by means of stud I2I, cause a rotation of the slide I22 about an axis through the stud I23. Inasmuch as the cam I26 remains stationary, roller I25 will move out of the central neutral position with respect to cam I26. e. g., roller I25 will move to the left or right and simultaneously the cam I26 will force this roller upward, increasing the tension upon spring I21. The increased tension upon the spring I21 will result in a greater vacuum within, the bellows 14, and consequently more vacuum will be applied to the centering valve 63.

13 Thus more vacuum will be applied to the bellows 52a or 52b as the wheel 30 is moved farther from its neutral position. The application of increased vacuum to the bellows 52a or 52b will, of course, result in an increase in the force resistin the movement of the control wheel 30 away from its neutral position. Consequently the greater the distance the control wheel 30 is moved from its neutral position, the greater will become the force opposing further movement of the control wheel.

For future reference, it should be noted that the cam roller I moves in a direction opposite the direction of movement of the wheel 30.

As far as the factor of the assumed air speed of the fuselage affecting the force resisting the movement of the control wheel is concerned, at this point it is simply stated that the greater the assumed air speed of the fuselage the greater is the vacuum within the air speed control loading regulator bellows 82. within the bellows 82, the greater will be the vacuum within the bellows 14 and consequently the greater will be the vacuum applied to the bellows 52a or 52b upon a movement of the control wheel 30 from its neutral position. Consequently the force resisting a movement of the control wheel 30 from its neutral position is dependent upon the vacuum within bellows 82 which in turn is dependent upon the assumed air speed of the fuselage. Means for operating the bellows 82 in response to changes in assumed air speed will hereinafter be disclosed.

The elevator trimming means which may form a part of my invention will now be described. Referring to Fig. 2, it will be seen that the manually rotatable elevator trimming member I30 is provided, this member being aflixed within the fuselage for rotation about the horizontal axis I3I. By means of a right angle drive I32 the screw I33 may be rotated in response to a rotation of the control I30. Rotation of the screw I33 results in an axial movement of the nut I 34 and a corresponding movement of the link I35, the rear end of which is attached to the nut I34 as shown. Movement of the link I35 results in a movement of the arms of bell crank I36 as well as in a movement of the link I31, the rear end of which is pivotally connected to the integral extension 61a of the center leaf 61 of the elevator centering valve 63.

Assuming that the student in the trainer finds that he must exert a constant fore or aft pressure upon the control wheel 30 in order to keep the fuselage in the desired climbing or diving position, it will be appreciated that simultaneously with the holding of the control wheel in the necessary position he will have displaced the upper leaf 68 of the elevator centering valve 63 a given distance from its neutral position. Instead of manually holding the control wheel 30 in the necessary off-center position to maintain the desired attitude of the fuselage, the student may hold the wheel 30 as required and simultaneously rotate the elevator trimming control I30 in the correct direction until the center leaf 61 of valve 63 again assumes a neutral position with respect to the upper leaf 68. In order to accomplish this result it will be appreciated that the center leaf 61 must be rotated in the same direction and through the same angle that the leaf 68 was rotated by the manual holding of the control wheel 30 from its neutral position. When the center leaf 61 has been rotated through this angle, it will be appreciated that it will prevent the application of excess vacuum and atmosphere to the The greater the vacuum rotating the trim control I30, and consequently the fuselage I2 remains in the same climbing,

diving or level flight position.

Specifically, it may be stated that if the student finds that he must exert a constant back pressure upon the wheel 30 to maintain the fuselage in the desired pitching position, wheel I30 is rotated counterclockwise, nut I34 travels ahead, and the center leaf 61a is rotated counterclockwise until the trimmed position is reached. If the student must exert a constant forward pressure, wheel I30 is rotated clockwise to the correct trimmed position.

Accordingly with the apparatus disclosed in Fig. 2 the student in the trainer may trim the fuselage so that he does not have to exert a constant pressure upon the control wheel 30 in order to keep the fuselage in the desired pitching attitude. It will be appreciated that this trimming of the trainer may be used by the student to climb or dive the trainer at a given angle or to fly the trainer at a constant altitude.

It will be appreciated by those skilled in the art of flying that the trimming of one of the control surfaces to relieve the pressure upon the control associated with that surface establishes a new position for the control at which no pressure is present upon the control. is then moved from this new position, a load is immediately placed upon the control, and the farther the control is moved from the trim-established zero pressure point, the greater becomes the pressure. If the control is released, the control surface and the control connected thereto return to the trim-established zero pressure point and not to the absolute neutral positions. The following means incorporated herein simulate this functioning of the control surfaces and controls of actual aircraft, as far as the elevator and fore and aft position of the wheel are concerned.

Referring to Fig. 2 it will be appreciated that as the nut I34 moves axially of the screw I 33, the link I40 moves therewith. The bell crank MI is turned and the transverse link I42 is moved resulting in a movement of the bell crank I43 and rearwardly extending link I44. The rear end of link I 44 is pivotally attached to the lower end of the cam I26 through the universal connector I44a, and, consequently, the cam I 26 moves whenever the elevator trimming control I30 is rotated. The movement of cam I26 will change the vertical position of roller I25 and consequently the tension upon spring I21.

Let us assume that the student must place the wheel 30 in a position to the rear of its neutral position in order to maintain the fuselage in the desired climbing attitude. In moving the wheel 30 from its neutral position it has been explained that the upper leaf of the valve 53 is rotated so as to admit vacuum to the bellows 52b and atmosphere to the bellows 52a. The elevator valve I I5 is operated to place the trainer in the desired climbing attitude and the movement to the rear of the wheel 30 simultaneously results in a movement toward the head of the trainer of the cam roller I25. The roller I25 is raised and the tension upon spring I21 is increasedthe fartherthe backward movement of wheel 30 the greater the relative motion between the roller I25 and As the control 15 the cam I 26. Then, when the student rota es the elevator trim control I36 counterclock se in order to move the leaf 61 of valve 63 to relieve the pressure upon the wheel 36, the link I44 simultaneously moves toward the rear of the trainer and the cam I26 rotates clockwise about the pivot I26. This rotation of the cam I26 allows spring I21 to pull the slide I22 and roller I25 downwardly, and when the leaf 61 is positioned by the student in the neutral position with respect to the leaf 68, the roller I25 is in the lowermost position with respect to cam I26. Thus the trimming of the trainer relaxes the tension which is placed upon the spring I21 when the wheel 30 is moved away from its neutral position so that when the elevator is properly trimmed, a normal or neutral tension is placed upon spring I21. As previously explained, the wheel 30 will remain displaced from its absolute neutral position and in the position in which the student had to hold the wheel to maintain the fuselage in the desired climbing position. Consequently, thereafter, should the student desire to move the wheel 36 farther to the rear, the pressure which he must exert upon the wheel is decreased by the amount that he removed when he had previously trimmed the trainer. Thus the trimming of the elevator by the student establishes a new neutral pressure point just as is the case in actual flight.

It will be appreciated that if the student finds he must hold the wheel forward to maintain the fuselage in the desired diving position, when he trims the fuselage he will establish a new zero pressure point.

In a. flight of actual aircraft equipped with elevator trimming means, the climbing and diving position of the plane may be controlled by a manipulation of the elevator trimming control. Thus, when it is desired to lower the nose of the plane the trim tab control may be rotated in the proper direction resulting in a movement of the elevator so that the nose drops. As the elevator moves, the control wheel moves to the fore. On the other hand, when it is desired to raise the nose of the plane, the trim control may be rotated in the opposite direction, the elevator moves in the opposite direction, and the nose of the plane rises. The wheel moves to the rear with the movement of the elevator. The previously disclosed simulated elevator trimming means of this invention may also be used to simulate this sometimes used method of controlling the climbing or diving attitude of a plane in actua1 flight.

Referring to Fig. 2, assuming that the wheel 30 and leaves of valve 63 are centered, if the student rotates the control I30 clockwise, the center leaf 61 of valve 63 is rotated clockwise admitting vacuum to the bellows 52b and air to the bellows 52a. The central bellows member 5'5 moves ahead, carrying with it the wheel 36, and the elevator valve H5 is operated to place the fuselage in a diving position. The forward movement of the member 56 simultaneously causes a clockwise rotation of the leaf 6B of valve 63. Bellows 5212 will be collapsed, moving member 5'5 ahead and rotating leaf 68 clockwise until this leaf is again neutrally positioned with respect to the leaf 61. When this position is reached the member 56 is stopped, the pressures within bellows 52a and 62 become neutralized, and the -wheel 36 is held ahead of its neutral position at a point depending upon angular movement of the simulated elevator trim control I30. The nose of the fuselage will be lowered as a result of the 75 fixed position the end members I65 of the two.

16" rotation of the upper leaf of the elevator valve An opposite rotation of the simulated elevator trim control I30 will produce reversed movements of the same parts of the apparatus just considered.

In view of the detailed disclosure of the preferred embodiment of my simulated elevator trimming means for use in grounded aviation trainers, is will be understood that I have provided apparatus which accomplishes the following results:

1. In the neutral position there is no load upon the control wheel, but as the wheel is moved ahead or to the rear of the neutral position, a load is immediately placed upon the wheel to resist the movement of the wheel and this load increases the fartherthe wheel is moved from its neutral position. The fuselage, simultaneously with a movement of the wheel from its neutral position, assumes the proper climbing or diving attitude.

2. When the wheel is moved from its neutral position the load placed upon the wheel is dependent upon the assumed air speed of the trainerthe higher the assumed air speed the greater the load.

3. The student may use the provided simulated elevator trimming means to relieve the pressure from the control wheel when he finds that he must exert a constant pressure upon the wheel in order to keep the trainer in the desired climbing or diving attitude. In using the simulated elevator trimming means the student holds the wheel in the correct position in order to maintain the correct climbing or diving attitude of the fuselage and then operates the simulated elevator trimming means until the pressure has been removed from the wheel, just as he would do in actual flight. When this point is reached the simulated elevator trimming means are properly positioned and the wheel is not moved as a result of the movement of the trimming means. The operation of the simulated elevator trimming means establishes a new neutral point insofar as pressure upon the wheel is concerned.

4. Alternatively, the simulated elevator trimming control may be used by the student to change the pitching attitude of the fuselage, just as the elevator trimming control in a real plane may be used to change the pitching attitude of the plane. When this method of operation is used the fore and aft position of the wheel as well as the position of the upper leaf of the elevator valve changes with the rotation of the simulated trimming control.

Simulated aileron loading and trimming means Reference is now made to Fig. 3 which discloses in detail the preferred embodiment of thesimulated aileron loading and trimming means which may form a part of my invention. In Fig. 3 the wheel 36 and main shaft 32 upon which the wheel is affixed are shown. A bracket IE6 is fixedly attached to the interior of the fuselage I2 some distance above the floor thereof and the bracket I6I is fixedly attached to the bracket I66. A plurality of upstanding members I62 integral with bracket I6I support the aileron control loading bellows assembly designated generally by I63. This bellows assembly, for all practical purposes, is identical with the elevator control loading bellows assembly shown in Fig. 2. A pair of side plates I64 are provided, these plates holding in a 

